In general, cellulose shaped articles (fiber, film, powder) are produced by mixing a solution, prepared by dissolving cellulose into a solvent by a certain type of method, into a nonsolvent. The methods for dissolving cellulose now used industrially for the above object include two methods: the viscose method found around 100 years ago (late 1890) wherein solid state alkali-cellulose is made by causing an around 20% aqueous alkali solution to act on the cellulose, causing carbon disulfide to react with this, then dissolving in an alkali and the cuprammonium method in which the cellulose is dissolved in a cuprammonium solution. The cellulose molecules in the solutions obtained by these methods do not dissolve in the form of cellulose, but dissolve as a certain cellulose derivative (cellulose xanthate in the viscous method and a cellulose cuprammonium complex in the cuprammonium method). Accordingly, when a cellulose shaped article is manufactured, it is necessary to use regeneration, i.e., a process in which the cellulose derivative is returned to cellulose, in addition to coagulation. For example, when producing a regenerated cellulose fiber, it has been known up to now that the setting of the conditions in the regeneration process is an important factor determining the physical properties of the obtained fiber. Thus, studies have been made to optimize the coagulating and regenerating conditions, aiming at superior physical properties, from various viewpoints, such as improvement of the dope, coagulation conditions (composition of coagulating bath, temperature of coagulation, length of coagulating bath, bath flow, nozzle). For example, mention can be made of the method of using a Muller bath, the polynosic method, the HW modulus method, the high tenacity rayon method, the Lilienfeld method using a concentrated sulfuric acid for the coagulating bath, etc. for the viscose rayon method and the free fall and stretch spinning method etc., for the cuprammonium method. In addition, as a method of dissolving cellulose, studies have focused on cadoxens (cadmium/ethylenediamine/alkali), nioxens (nickel/ethylenediamine/alkali), EWNN (iron/tartaric acid/alkali), and other metal complexes, but these are not superior to the cuprammonium method and the viscose method in terms of safety and economy. Also, neither of the above methods can avoid the generation of toxic gases or discharge of heavy metals in the process of preparation of the solutions or the process of production of the shaped articles, and therefore, have problems when viewed from the standpoint of the work environment or the global environment.
That is, (1) these make use of carbon disulfide and ammonium, which have an adverse effect on the human body, and these have explosive limits. (2) They include copper, which is a heavy metal, and produce harmful waste gas in the processes of dissolution/coagulation/regeneration/scouring, so a vast amount of energy and water are required for their reclamation/purification/disposal, the process becomes longer, and the facilities become longer and larger. (3) Due to (1) and (2), the regenerated cellulose fiber industry must inevitably become a labor-intensive type production style.
On the other hand, voices arose, mostly in the West, from the 1960s to the 1970s warning of the continued industrial use of traditional techniques like the viscose method and the cuprammonium method. The first wave of this which appeared most remarkably was with the pullout of many companies from the viscose rayon business. The second wave has been with the now under way movement toward restriction of discharge and the prohibition of use of harmful substances due to the global scale environmental problems, such as seen in the Environmental Summit. With the above as a background, research has been under way since the 1970s, primarily in Canada and the United States, reevaluating the existing method of dissolution of cellulose and calling for obtaining novel regenerated cellulose shaped articles by dissolving cellulose directly in an organic solvent so as to close off the fiber and film producing process. As a result, numerous methods of dissolution have actually been discovered, but all of these use solvents and salts comprised of complicated, numerous components. Due to the higher costs, toxicity, explosiveness, difficulties of solvent recovery, etc., of the solvent itself, there have been very few actual cases of commercialization (industrialization) of these. Further, these newly discovered methods of dissolution almost all convert the cellulose into a certain form of derivative and then dissolve that derivative in a suitable solvent, so in that sense are not greatly different technically speaking from the viscose method or the cuprammonium method in any way. In this way, in the case of spinning cellulose by an organic solvent, there is the advantage that no use is made of heavy metals or volatile gases, but there are the serious problems from the industrial viewpoint that (1) most methods are accompanied with chemical reactions at the time of dissolution, and therefore, so in the dissolved state, the cellulose is dissolved in the form of a derivative and either byproducts (modifications of the solvent itself) are produced at the time of regeneration or regeneration is not possible and the shaped article ends up comprised of the cellulose derivative as it is, (2) since the solvent itself is high in price, a high reclamation rate is required or since most solvents have high boiling points, the energy costs become higher and further loss is unavoidable due to the denaturation accompanying the reaction/regeneration, (3) the solvent itself is highly toxic and explosive, etc.
On the other hand, running counter to these trends, as shown in Japanese Unexamined Patent Publication No. 62-240328 and 62-620329, two or three attempts are being made to produce cellulose shaped articles by environmental-friendly processes. These disclose methods for producing cellulose shaped articles nonpollutingly, i.e., the cellulose is subjected to physical treatment such as steam explosion treatment to make it soluble in alkali, then is dissolved in an aqueous alkali solution and wet molded, with no use of carbon disulfide, heavy metals, organic solvents, or other harmful substances at all. The control of the cohesive structure during the coagulation, for example, the control for achieving a fine cohesion during coagulation or deformation of the coagulating gel, is extremely difficult, however, and the physical properties of the resultant cellulose shaped articles also were not fully satisfactory. This suggests that, basically, in the case of using a dope comprised of just a cellulose and an alkali, the structural control in the molding process is difficult since there is no regeneration process, which had been an important factor in the control of physical properties in the shaping process based on conventional methods (viscose method and cuprammonium method).